Water quality -- Uranium isotopes -- Test method using alpha-spectrometry

This document specifies the conditions for the determination of uranium isotope activity concentration in samples of environmental water (including sea waters) using alpha-spectrometry and 232U as a yield tracer. A chemical separation is required to separate and purify uranium from a test portion of the sample.

Qualité de l'eau -- Isotopes de l'uranium -- Méthode d'essai par spectrométrie alpha

Le présent document spécifie les conditions relatives ŕ la détermination de l'activité volumique des isotopes de l'uranium dans des échantillons d'eau environnementale (y compris les eaux de mer) par spectrométrie alpha en utilisant 232U comme traceur. Une séparation chimique est requise pour séparer et purifier l'uranium de la prise d'essai.

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Publication Date
03-Aug-2020
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5060 - Close of voting Proof returned by Secretariat
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Completion Date
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INTERNATIONAL ISO
STANDARD 13166
Second edition
2020-08
Water quality — Uranium isotopes —
Test method using alpha-spectrometry
Qualité de l'eau — Isotopes de l'uranium — Méthode d'essai par
spectrométrie alpha
Reference number
ISO 13166:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO 13166:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
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CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 13166:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms, definitions and symbols ............................................................................................................................................................ 1

4 Principle ........................................................................................................................................................................................................................ 2

5 Chemical reagents and equipment .................................................................................................................................................... 3

5.1 General ........................................................................................................................................................................................................... 3

5.2 Chemical reagents ................................................................................................................................................................................ 3

5.3 Equipment ................................................................................................................................................................................................... 4

6 Sampling and samples .................................................................................................................................................................................... 4

6.1 Sampling ....................................................................................................................................................................................................... 4

6.2 Sample storage ........................................................................................................................................................................................ 4

7 Separation and measurement ................................................................................................................................................................ 5

7.1 Chemical steps ......................................................................................................................................................................................... 5

7.2 Measurement ............................................................................................................................................................................................ 5

7.2.1 Quality control ................................................................................................................................................................... 5

7.2.2 Chemical yield .................................................................................................................................................................... 5

7.2.3 Background........................................................................................................................................................................... 5

8 Expression of results ........................................................................................................................................................................................ 6

8.1 Spectrum analysis ................................................................................................................................................................................ 6

8.2 Calculation of activity concentration ................................................................................................................................... 6

8.3 Standard uncertainty ......................................................................................................................................................................... 6

8.4 Decision threshold ............................................................................................................................................................................... 7

8.5 Detection limit ......................................................................................................................................................................................... 7

8.6 Limits of the coverage interval .................................................................................................................................................. 8

8.6.1 Limits of the probabilistically symmetric coverage interval...................................................... 8

8.6.2 The shortest coverage interval ............................................................................................................................ 8

9 Test report ................................................................................................................................................................................................................... 9

Annex A (informative) Chemical separation of uranium ..............................................................................................................10

Annex B (informative) Precipitation of the source by electrodeposition ...................................................................13

Annex C (informative) Preparation of the source by coprecipitation .............................................................................16

Annex D (informative) Occurrence of uranium isotopes ..............................................................................................................18

Bibliography .............................................................................................................................................................................................................................19

© ISO 2020 – All rights reserved iii
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ISO 13166:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 3,

Radiological methods.

This second edition cancels and replaces the first edition (ISO 13166:2014), of which it constitutes a

minor revision. The changes compared to the previous edition are as follows:
— update of the common introduction;
— update of the text considering the new ISO 11929 series published in 2019.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved
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ISO 13166:2020(E)
Introduction

Radioactivity from several naturally occurring and anthropogenic sources is present throughout

the environment. Thus, water bodies (e.g. surface waters, ground waters, sea waters) can contain

radionuclides of natural, human-made, or both origins:
40 3 14

— Natural radionuclides, including K, H, C, and those originating from the thorium and uranium

226 228 234 238 210

decay series, in particular Ra, Ra, U, U, and Pb, can be found in water for natural reasons

(e.g. desorption from the soil and wash off by rain water) or can be released from technological

processes involving naturally occurring radioactive materials (e.g. the mining and processing of

mineral sands or phosphate fertilizer production and use);

— Human-made radionuclides, such as transuranium elements (americium, plutonium, neptunium,

3 14 90

curium), H, C, Sr, and gamma emitting radionuclides can also be found in natural waters.

Small quantities of these radionuclides are discharged from nuclear fuel cycle facilities into the

environment as the result of authorized routine releases. Some of these radionuclides used for

medical and industrial applications are also released into the environment after use. Anthropogenic

radionuclides are also found in waters as a result of past fallout contaminations resulting from

the explosion in the atmosphere of nuclear devices and accidents such as those that occurred in

Chernobyl and Fukushima.

Radionuclide activity concentration in water bodies can vary according to local geological

characteristics, and climatic conditions and can be locally and temporally enhanced by releases from

[1]

nuclear installation during planned, existing and emergency exposure situations . Drinking-water

may thus contain radionuclides at activity concentrations which could present a risk to human health.

The radionuclides present in liquid effluents are usually controlled before being discharged into

[2]

the environment and water bodies. Drinking water is monitored for its radioactivity content as

[3]

recommended by the World Health Organization (WHO) so that proper actions can be taken to ensure

that there is no adverse health effects to the public. Following these international recommendations,

national regulation usually specify radionuclide authorized concentration limits for liquid effluent

discharged to the environment and radionuclide guidance levels for water bodies and drinking waters

for planned, existing and emergency exposure situations. Compliance with these limits can be assessed

using measurement results with their associated uncertainties as specified by ISO/IEC Guide 98-3 and

[4]
ISO 5667-20 .

Depending on the exposure situation, there are different limits and guidance levels that would result

in an action to reduce health risk. As an example, during a planned or existing situation, the WHO

238 234 -1

guidance level in drinking water for U and U is 10 and 1 Bq · l , respectively. The provisional

guideline value for the concentration of uranium in drinking water is 30 μg · l based on its chemical

toxicity, which is predominant compared with its radiological toxicity.

NOTE 1 The guidance level is the activity concentration with an intake of 2 l/d of drinking water for one year

that results in an effective dose of 0,1 mSv/a for members of the public. This is an effective dose that represents a

[3]

very low level of risk and which is not expected to give rise to any detectable adverse health effects .

[5]

In the event of a nuclear emergency, the WHO Codex Guideline Levels mentioned that the activity

concentration might be greater.

NOTE 2 The Codex guidelines levels (GLs) apply to radionuclides contained in foods destined for human

consumption and traded internationally, which have been contaminated following a nuclear or radiological

emergency. These GLs apply to food after reconstitution or as prepared for consumption, i.e., not to dried or

concentrated foods, and are based on an intervention exemption level of 1 mSv in a year for members of the

[5]
public (infant and adult) .

Thus, the test method can be adapted so that the characteristic limits, decision threshold, detection

limit and uncertainties ensure that the radionuclide activity concentrations test results can be verified

to be below the guidance levels required by a national authority for either planned/existing situations

[6][7]
or for an emergency situation .
© ISO 2020 – All rights reserved v
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ISO 13166:2020(E)

Usually, the test methods can be adjusted to measure the activity concentration of the radionuclide(s)

in either wastewaters before storage or in liquid effluents before being discharged to the environment.

The test results will enable the plant/installation operator to verify that, before their discharge,

wastewaters/liquid effluent radioactive activity concentrations do not exceed authorized limits.

The test method(s) described in this document may be used during planned, existing and emergency

exposure situations as well as for wastewaters and liquid effluents with specific modifications that

could increase the overall uncertainty, detection limit, and threshold.

The test method(s) may be used for water samples after proper sampling, sample handling, and test

sample preparation (see the relevant part of the ISO 5667 series).

This document has been developed to answer the need of test laboratories carrying out these

measurements that are sometimes required by national authorities, as they may have to obtain a

specific accreditation for radionuclide measurement in drinking water samples.

This document is one of a family of International Standards on test methods dealing with the

measurement of the activity concentration of radionuclides in water samples.
vi © ISO 2020 – All rights reserved
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INTERNATIONAL STANDARD ISO 13166:2020(E)
Water quality — Uranium isotopes — Test method using
alpha-spectrometry

WARNING — Persons using this document should be familiar with normal laboratory practices.

This document does not purport to address all of the safety problems, if any, associated with its

use. It is the responsibility of the user to establish appropriate safety and health practices and to

determine the applicability of any other restrictions.

IMPORTANT — It is absolutely essential that tests conducted according to this document be

carried out by suitably trained staff.
1 Scope

This document specifies the conditions for the determination of uranium isotope activity concentration

232

in samples of environmental water (including sea waters) using alpha-spectrometry and U as a

yield tracer.

A chemical separation is required to separate and purify uranium from a test portion of the sample.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 3696, Water for analytical laboratory use — Specification and test methods

ISO 5667-1, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes and

sampling techniques

ISO 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples

ISO 11929-1, Determination of the characteristic limits (decision threshold, detection limit and limits of

the coverage interval) for measurements of ionizing radiation — Fundamentals and application — Part 1:

Elementary applications

ISO 11929-3, Determination of the characteristic limits (decision threshold, detection limit and limits of

the coverage interval) for measurements of ionizing radiation — Fundamentals and application — Part 3:

Applications to unfolding methods
ISO 80000-10, Quantities and units — Part 10: Atomic and nuclear physics

ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in

me a s ur ement (GUM: 1995)

ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories

3 Terms, definitions and symbols

For the purposes of this document, the terms, definitions, and symbols given in ISO 80000-10,

ISO 11929-1 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at http:// www .electropedia .org/
© ISO 2020 – All rights reserved 1
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ISO 13166:2020(E)
— ISO Online browsing platform: available at http:// www .iso .org/ obp
Table 1 — Symbols and definitions
Symbol Definition
232
A activity of U tracer added, in becquerel, at the date of measurement
238 235 234
c activity concentration of U or U or U, in becquerels per litre
decision threshold, in becquerels per litre
# detection limit, in becquerels per litre

lower and upper limits of the probabilistically symmetric coverage interval, in becquerels per litre

cc,
< >

c , c lower and upper limits of the shortest coverage interval, in becquerels per litre

A A
R total measurement yield

r , r background count rate per second for the uranium analytes and tracer in the respective regions

0 0T
of interest (ROI) of the blank sample spectrum
R chemical yield

r , r gross count rate per second for the uranium analytes and tracer in the respective regions of

g gT
interest (ROI) of the test sample spectrum
t background counting time, in seconds
t sample counting time, in seconds

U expanded uncertainty, calculated by U = ku(c ) with k = 1, 2 …, in becquerels per litre

u(c ) standard uncertainty associated with the measurement result; in becquerels per litre

V volume of test sample, in litres
ε counting efficiency
4 Principle
232

The test sample is mixed with an aliquot of U tracer, followed by equilibration of the sample prior

to analysis. Chemical isolation of uranium is achieved by a concentration step (e.g. a precipitation)

followed by a specific separation step (e.g. using ion exchange chromatography).

The detection limit for measurement of a test portion of about 500 ml is approximately 5 mBq · l with

a counting time of about 200 000 s.
230 226 228

Natural radionuclides such as Th, Ra and Th can be present in water and can interfere with the

counting of uranium isotopes if no chemical separation is carried out to remove these radionuclides from

the test portion. Plutonium isotopes can also interfere, if present with detectable activities in the sample.

The measured thin source is prepared by electrodeposition or coprecipitation and measured by alpha-

spectrometry using a grid chamber or a semiconductor-type apparatus. Measurements rely on the

interaction of alpha-particles with the detecting medium. This interaction creates a charge, which is

amplified and output as a voltage pulse proportional to the deposited energy of the incoming alpha-

particle.

The electric pulse from the detector is analysed by the electronic systems. Data analysis software

provides a spectrum, in which the number of pulses (counts) recorded in each energy interval is shown.

The analysis of the count rates in the uranium isotopes alpha-energy windows allows the determination

238 235 234

of the test sample activity concentration for U, U and U, after correcting for the blank count rate,

volume of the test sample and the total measurement yield (chemical yield and detection efficiency).

The chemical yield and detection efficiency are not necessarily determined separately, but are

232

determined together by measuring the total measurement yield from the net count rate of U, added

as a chemical yield tracer.
2 © ISO 2020 – All rights reserved
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ISO 13166:2020(E)

In order to quantify any potential interference coming from the reagents, a blank sample is prepared in

the same way as the test sample. This blank sample is prepared using a laboratory water.

For quality control, in order to quantify potential impurities in the tracer solution, another blank sample

shall be prepared with addition of tracer.

The radioactive characteristics of the main uranium isotopes are given in Table 2 (References [8], [9]).

Table 2 — Radioactive characteristics of the main uranium isotopes
Uranium Half-life Main emission energy Intensity
isotope years keV %
5 263,48 30,6
232 70,6 (±1,1)
5 320,24 69,1
4 783,5 13,2
233 159,1 (±0,2) × 10
4 824,2 84,3
4 722,4 28,42
234 2,455 (±0,006) × 10
4 774,6 71,37
4 366,1 18,8
235 704 (±1) × 10 4 397,8 57,19
4 414,9 3.01
4 445 26,1
236 23,43 (±0,06) × 10
4 494 73,8
4 151 22,33
238 4,468(±0,005) × 10
4 198 77,54

With a spectral resolution (FWHM full-width half-maximum height) of around 20 keV in best cases,

233 234 235 236

alpha-spectrometry cannot easily resolve U and U, nor U and U, due to the similarity in

233 236

their respective emission energies. However, U and U are normally not present in environmental

samples or in quantities above their detection limits using alpha spectrometry (see Annex D).

5 Chemical reagents and equipment
5.1 General

The chemical reagents and equipment used for chemical treatment and preparation of the source are

described in Annexes A to C, which give various alternatives. Where there are options, at least one of

the options presented shall be used.
Use only reagents of recognized analytical grade.
5.2 Chemical reagents

5.2.1 Laboratory water, used as a blank, as free as possible of chemical or radioactive impurities

(e.g. uranium isotopes), conforming to ISO 3696, grade 3.

Fresh rainwater is an example of water with a very low uranium activity concentration. The uranium

activity concentration of this water can be evaluated at the same time as interferences from reagents or

using another type of precise measurement, e.g. thermal ionization or inductively coupled plasma mass

spectrometry.
© ISO 2020 – All rights reserved 3
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ISO 13166:2020(E)
232

5.2.2 U tracer solution, used to determine the total yield. It can also be used to calculate the chemical

yield. The solution is prepared by the dilution of a suitable standard that provides traceability to national

and international standards. The tracer solution shall be homogeneous and stable.

The tracer solution concentration should be calculated to allow adding a small amount of this solution

in order to be in the range of activity contained in the test portion. For example, the tracer solution

−1 −1
concentration could be between 0,05 Bq · g and 1 Bq · g .

It is recommended that the activity and the purity of the tracer solution dilution be checked before

use and at regular intervals after preparation. This can be done, for example, by liquid scintillation

counting, but account needs to be taken of progeny radionuclide ingrowth. Performing a blank analysis

with tracer is a potential way to identify any presence of uranium isotope analytes in the tracer.

228 232

Th is present in the U tracer solution as a member of its decay series and has very close energy to

232

that of U. Therefore, separation between Th and U is required (References [10], [11]) to minimize the

228 232

interference of Th so that the counting yield of U is not overestimated (see Clause 4).

5.3 Equipment
Usual laboratory apparatus and in particular the following:

5.3.1 Alpha-spectrometer, of the grid chamber (with higher detection yield, but lower resolution)

or semiconductor type (with lower detection yield, but higher resolution). Operation at constant

temperature is recommended. Follow the manufacturer's instructions.

For semiconductor-type apparatus, the measurements using alpha-spectrometry depend on the

interaction of alpha-particles with ion-implanted silicon. This interaction instantly changes the

conductivity of the silicon, proportional to the energy of the incoming alpha-particle. To achieve well-

resolved spectra, the detection system needs to be maintained at a pressure <1 Pa. Resolution can be

further enhanced through increasing distance between source and detector.
232

5.3.2 Pipette, suitable for the accurate transfer of (for example 100 µl) U tracer solution with a total

precision within ±1 %.
5.3.3 Balance, for example, capable of achieving ±0,1 mg precision.
6 Sampling and samples
6.1 Sampling
Conditions of sampling shall conform to ISO 5667-1.

Filter the sample to remove solids and then acidify to < pH 2 with nitric acid or hydrochloric acid as soon

as possible after sampling prior to analysis, as specified in ISO 5667-3. Acidification prior to filtration

can result in leaching of uranium from solids component of sample.

It is important that the laboratory receive a representative sample, unmodified during transport or

storage and in an undamaged container.
6.2 Sample storage
If required, the sample is shall be stored according to ISO 5667-3.
4 © ISO 2020 – All rights reserved
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ISO 13166:2020(E)
7 Separation and measurement
7.1 Chemical steps

Suggested separation and source preparation strategies are outlined in Annexes A, B, and C respectively.

7.2 Measurement
7.2.1 Quality control

Equipment quality control sources shall be measured to verify that the measurement equipment is

performing within agreed limits.
239/240 230 239 244 241
A thin source of Pu (other alpha-emitters such as Th, Pu, Cm, and Am are also

possible) may be employed to check the energy calibration and the energy resolution (alpha-emissions

are in the 5,10 MeV to 5,20 MeV energy region), and there is no appreciable decay over the working life

of the source.
7.2.2 Chemical yield

The chemical yield can be considered as a quality control parameter. In general, the chemical yield

obtained is around 90 %. For very low chemical yields, it is recommended to redo the sample analysis.

The chemical yield R of the process can be calculated using Formula (1):
R = (1)

Total yield R is the product of the chemical yield and the counting efficiency ε.

Total yield, R, is calculated from the sample spectrum using Formula (2):
rr−
gT 0T
R= (2)
7.2.3 Background

The background rate of each detector is determined with an empty source support with the lowest

activity possible present on, this shall take at least as much time as the counting of a sample.

The optimum time for the measurement of the background source can be shown to be equal to that of

the source from very low activity sources.

The blank sample analysis (i.e. analysis carried out with laboratory water containing no detectable

uranium isotope without adding tracer) value shall be compared to the totality of the background

values obtained from the same detector.

This value can be comparable to the background value measured with an empty source support in the

energy regions of uranium isotopes and of the tracer if there is no reagent or laboratory equipment

contamination.
r is the blank value or can be the background value of the detector if similar.
© ISO 2020 – All rights reserved 5
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ISO 13166:2020(E)
8 Expression of results
8.1 Spectrum analysis
...

NORME ISO
INTERNATIONALE 13166
Deuxième édition
2020-08
Qualité de l'eau — Isotopes de
l'uranium — Méthode d'essai par
spectrométrie alpha
Water quality — Uranium isotopes — Test method using alpha-
spectrometry
Numéro de référence
ISO 13166:2020(F)
ISO 2020
---------------------- Page: 1 ----------------------
ISO 13166:2020(F)
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2020

Tous droits réservés. Sauf prescription différente ou nécessité dans le contexte de sa mise en œuvre, aucune partie de cette

publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique,

y compris la photocopie, ou la diffusion sur l’internet ou sur un intranet, sans autorisation écrite préalable. Une autorisation peut

être demandée à l’ISO à l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.

ISO copyright office
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CH-1214 Vernier, Genève
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Publié en Suisse
ii © ISO 2020 – Tous droits réservés
---------------------- Page: 2 ----------------------
ISO 13166:2020(F)
Sommaire Page

Avant‑propos ..............................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Domaine d’application ................................................................................................................................................................................... 1

2 Références normatives ................................................................................................................................................................................... 1

3 Termes, définitions et symboles .......................................................................................................................................................... 1

4 Principe .......................................................................................................................................................................................................................... 2

5 Réactifs chimiques et matériel .............................................................................................................................................................. 3

5.1 Généralités .................................................................................................................................................................................................. 3

5.2 Réactifs chimiques ............................................................................................................................................................................... 4

5.3 Matériel ......................................................................................................................................................................................................... 4

6 Échantillonnage et échantillons ........................................................................................................................................................... 4

6.1 Échantillonnage ...................................................................................................................................................................................... 4

6.2 Conservation des échantillons ......... .......................................................................................................................................... 5

7 Séparation et mesurage ................................................................................................................................................................................ 5

7.1 Étapes chimiques .................................................................................................................................................................................. 5

7.2 Mesurage ...................................................................................................................................................................................................... 5

7.2.1 Contrôle de la qualité ................................................................................................................................................... 5

7.2.2 Rendement chimique ................................................................................................................................................... 5

7.2.3 Bruit de fond ........................................................................................................................................................................ 5

8 Expression des résultats............................................................................................................................................................................... 6

8.1 Analyse du spectre ............................................................................................................................................................................... 6

8.2 Calcul de l’activité volumique..................................................................................................................................................... 6

8.3 Incertitude-type ..................................................................................................................................................................................... 6

8.4 Seuil de décision .................................................................................................................................................................................... 7

8.5 Limite de détection .............................................................................................................................................................................. 7

8.6 Limites des intervalles élargis ................................................................................................................................................... 8

8.6.1 Limites de l’intervalle élargi probabilistiquement symétrique ............................................... 8

8.6.2 Intervalle élargi le plus court ................................................................................................................................ 8

9 Rapport d’essai ....................................................................................................................................................................................................... 9

Annexe A (informative) Séparation chimique de l’uranium .....................................................................................................10

Annexe B (informative) Préparation de la source par électrodéposition ...................................................................14

Annexe C (informative) Préparation de la source par co‑précipitation ........................................................................17

Annexe D (informative) Occurrence des isotopes de l’uranium ...........................................................................................19

Bibliographie ...........................................................................................................................................................................................................................20

© ISO 2020 – Tous droits réservés iii
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ISO 13166:2020(F)
Avant‑propos

L'ISO (Organisation internationale de normalisation) est une fédération mondiale d'organismes

nationaux de normalisation (comités membres de l'ISO). L'élaboration des Normes internationales est

en général confiée aux comités techniques de l'ISO. Chaque comité membre intéressé par une étude

a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,

gouvernementales et non gouvernementales, en liaison avec l'ISO participent également aux travaux.

L'ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui

concerne la normalisation électrotechnique.

Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont

décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier, de prendre note des différents

critères d'approbation requis pour les différents types de documents ISO. Le présent document a été

rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir www

.iso .org/ directives).

L'attention est attirée sur le fait que certains des éléments du présent document peuvent faire l'objet de

droits de propriété intellectuelle ou de droits analogues. L'ISO ne saurait être tenue pour responsable

de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant

les références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de

l'élaboration du document sont indiqués dans l'Introduction et/ou dans la liste des déclarations de

brevets reçues par l'ISO (voir www .iso .org/ brevets).

Les appellations commerciales éventuellement mentionnées dans le présent document sont données

pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un

engagement.

Pour une explication de la nature volontaire des normes, la signification des termes et expressions

spécifiques de l'ISO liés à l'évaluation de la conformité, ou pour toute information au sujet de l'adhésion

de l'ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les obstacles

techniques au commerce (OTC), voir www .iso .org/ avant -propos.

Le présent document a été élaboré par le comité technique ISO/TC 147, Qualité de l'eau, sous-comité

SC 3, Mesurages de la radioactivité.

Cette deuxième édition annule et remplace la première édition (ISO 13166:2014), dont elle constitue

une révision mineure. Les modifications apportées par rapport à l’édition précédente sont les suivantes:

— mise à jour de l’introduction commune;

— mise à jour du texte suite à la publication de la série de normes ISO 11929 publiées en 2019.

Il convient que l’utilisateur adresse tout retour d’information ou toute question concernant le présent

document à l’organisme national de normalisation de son pays. Une liste exhaustive desdits organismes

se trouve à l’adresse www .iso .org/ fr/ members .html.
iv © ISO 2020 – Tous droits réservés
---------------------- Page: 4 ----------------------
ISO 13166:2020(F)
Introduction

La radioactivité provenant de sources d’origine naturelle et anthropique est présente partout dans

l’environnement. Par conséquent, les masses d’eau (par exemple eaux de surface, eaux souterraines, eau

de mer) peuvent contenir des radionucléides d’origine naturelle et/ou engendrés par l’homme:

40 3 14

— les radionucléides naturels, y compris K, H et C, et ceux provenant des chaînes de désintégration

226 228 234 238 210

du thorium et de l’uranium, notamment Ra, Ra, U, U et Pb, peuvent se trouver dans l’eau

pour des raisons naturelles (par exemple, désorption par le sol et lessivage par les eaux pluviales) ou

peuvent être libérés par des processus technologiques impliquant des matériaux radioactifs existant

à l’état naturel (par exemple, extraction minière et traitement de sables minéraux ou production et

utilisation d’engrais phosphatés);

— les radionucléides artificiels, tels que les éléments transuraniens (américium, plutonium, neptunium,

3 14 90

curium), H, C, Sr et des radionucléides émetteurs gamma peuvent aussi se trouver dans les eaux

naturelles. De faibles quantités de ces radionucléides sont rejetées dans l’environnement dans le

cadre de rejets réguliers autorisés par les installations en lien avec le cycle du combustible nucléaire.

Certains de ces radionucléides, utilisés dans le cadre d’applications médicales et industrielles, sont

également libérés dans l’environnement après usage. Les radionucléides anthropiques peuvent

également se trouver dans l’eau du fait de la pollution par retombées d’éléments radioactifs rejetés

dans l’atmosphère lors de l’explosion de dispositifs nucléaires ou lors d’accidents nucléaires tels que

Tchernobyl et Fukushima.

L’activité volumique d’un radionucléide dans les masses d’eau peut varier selon les caractéristiques

géologiques et les conditions climatiques locales, et peut augmenter temporairement au niveau

local suite aux rejets d’installations nucléaires lors de situations d’exposition prévues, existantes

[1]

ou d’urgence . L’eau potable peut donc contenir des radionucléides dont l’activité volumique est

susceptible de présenter un risque pour la santé humaine.

Les radionucléides présents dans les effluents liquides sont généralement contrôlés avant leur rejet

[2]

dans l’environnement et les masses d’eau. La teneur en radioactivité de l’eau potable est surveillée

[3]

conformément aux recommandations de l’Organisation mondiale de la Santé (OMS) afin de pouvoir

prendre les mesures nécessaires pour garantir l’absence d’effets indésirables sur la santé publique.

Suite à ces recommandations internationales, la réglementation nationale précise habituellement

les concentrations limites de radionucléides autorisées pour les effluents liquides rejetés dans

l’environnement ainsi que les limites indicatives de radionucléides pour les masses d’eau et les eaux de

boisson lors de situations d’exposition prévues, existantes ou d’urgence. Le respect de ces limites peut

être vérifié à l’aide de résultats de mesurage et des incertitudes associées obtenus conformément au

[4]
Guide ISO/IEC 98-3 et à l’ISO 5667-20 .

En fonction de la situation à l’origine de l’exposition, il existe plusieurs limites et niveaux recommandés

susceptibles de déclencher une action visant à réduire le risque sanitaire. Par exemple, lors d’une

238 234

situation prévue ou existante, la limite indicative concernant l’activité volumique de U et U dans

l’eau potable, conformément aux recommandations de l’OMS, est respectivement de 10 et 1 Bq· l . La

limite indicative provisoire concernant la concentration en uranium dans l’eau potable est de 30 μg · l ,

en se basant sur sa toxicité chimique, qui est prédominante par rapport à sa toxicité radiologique.

NOTE 1 La limite indicative correspond à l’activité volumique avec incorporation de 2 l/j d’eau potable pendant

1 an, aboutissant à une dose efficace de 0,1 mSv/an pour les personnes du public. Cette dose efficace présente un

[3]

niveau de risque très faible qui ne devrait pas entraîner d’effets indésirables détectables sur la santé .

[5]

Les limites indicatives du codex de l’OMS mentionnent que l’activité volumique peut être supérieure

en cas de situation d’urgence d’origine nucléaire.

NOTE 2 Les limites indicatives énoncées dans le codex s’appliquent aux radionucléides contenus dans les

aliments destinés à la consommation humaine et commercialisés à l’échelle internationale qui ont été contaminés

suite à une situation d’urgence de type nucléaire ou radiologique. Ces limites indicatives s’appliquent aux

aliments après reconstitution ou tels que préparés pour la consommation; autrement dit, elles ne s’appliquent

pas aux aliments séchés ou concentrés et elles sont basées sur un niveau d’exemption d’intervention de 1 mSv/an

[5]
pour les membres du public (enfants et adultes) .
© ISO 2020 – Tous droits réservés v
---------------------- Page: 5 ----------------------
ISO 13166:2020(F)

Ainsi, la méthode d’essai peut être adaptée de telle sorte que les limites caractéristiques, le seuil de

décision, la limite de détection et les incertitudes garantissent qu’il soit possible de vérifier que les

résultats des essais portant sur l’activité volumique des radionucléides sont inférieurs aux limites

indicatives requises par une autorité nationale pour les situations planifiées/existantes ou pour une

[6][7]
situation d’urgence .

Généralement, les méthodes d’essai peuvent être ajustées pour mesurer l’activité volumique du ou

des radionucléides dans les eaux usées avant stockage, ou dans les effluents liquides avant rejet dans

l’environnement. Les résultats d’essai permettent à l’exploitant de l’installation industrielle de vérifier,

avant rejet, que les activités volumiques des radionucléides présents dans les eaux usées/dans l’effluent

liquide ne dépassent pas les limites autorisées.

La ou les méthodes d’essai décrites dans le présent document peuvent être utilisées lors de situations

d’exposition prévues, existantes ou d’urgence, ainsi que pour les eaux usées et effluents liquides, avec

des modifications spécifiques susceptibles d’augmenter l’incertitude, la limite de détection et le seuil

globaux.

La ou les méthodes d’essai peuvent être utilisées pour les échantillons d’eau après prélèvement

et manipulation appropriés des échantillons et préparation de la prise d’essai (voir la partie

correspondante de la série de l’ISO 5667).

Le présent document a été élaboré pour répondre au besoin des laboratoires d’essai réalisant ces

mesurages et qui sont parfois tenus d’obtenir une accréditation spécifique de la part d’autorités

nationales pour la réalisation de mesurages portant sur les radionucléides dans les échantillons d’eau

potable.

Le présent document fait partie d’une série de Normes internationales portant sur des méthodes d’essai

visant à mesurer de l’activité volumique des radionucléides dans des échantillons d’eau.

vi © ISO 2020 – Tous droits réservés
---------------------- Page: 6 ----------------------
NORME INTERNATIONALE ISO 13166:2020(F)
Qualité de l'eau — Isotopes de l'uranium — Méthode
d'essai par spectrométrie alpha

AVERTISSEMENT — Il convient que les utilisateurs du présent document connaissent les

pratiques courantes de laboratoire. Le présent document n’a pas la prétention d’aborder tous

les éventuels problèmes de sécurité liés à son utilisation. Il incombe à l’utilisateur d’établir des

pratiques appropriées en matière de santé et de sécurité et de déterminer l’applicabilité de toute

autre restriction éventuelle.

IMPORTANT — Il est absolument essentiel que les essais réalisés conformément au présent

document soient effectués par du personnel qualifié.
1 Domaine d’application

Le présent document spécifie les conditions relatives à la détermination de l’activité volumique des

isotopes de l’uranium dans des échantillons d’eau environnementale (y compris les eaux de mer) par

232
spectrométrie alpha en utilisant U comme traceur.

Une séparation chimique est requise pour séparer et purifier l’uranium de la prise d’essai.

2 Références normatives

Les documents suivants sont cités dans le texte de sorte qu’ils constituent, pour tout ou partie de leur

contenu, des exigences du présent document. Pour les références datées, seule l’édition citée s’applique.

Pour les références non datées, la dernière édition du document de référence s’applique (y compris les

éventuels amendements).

ISO 3696, Eau pour laboratoire à usage analytique — Spécification et méthodes d'essai

ISO 5667-1, Qualité de l’eau — Échantillonnage — Partie 1: Lignes directrices pour la conception des

programmes et des techniques d’échantillonnage

ISO 5667-3, Qualité de l'eau — Échantillonnage — Partie 3: Conservation et manipulation des

échantillons d'eau

ISO 11929-1, Détermination des limites caractéristiques (seuil de décision, limite de détection et

extrémités de l'intervalle élargi) pour mesurages de rayonnements ionisants — Principes fondamentaux et

applications — Partie 1: Applications élémentaires

ISO 11929-3, Détermination des limites caractéristiques (seuil de décision, limite de détection et

extrémités de l'intervalle élargi) pour mesurages de rayonnements ionisants — Principes fondamentaux et

applications — Partie 3: Applications aux méthodes de déconvolution
ISO 80000-10, Grandeurs et unités — Partie 10: Physique atomique et nucléaire

Guide ISO/IEC 98-3, Incertitude de mesure — Partie 3: Guide pour l’expression de l’incertitude de mesure

(GUM: 1995)

ISO/IEC 17025, Exigences générales concernant la compétence des laboratoires d'étalonnages et d'essais

3 Termes, définitions et symboles

Pour les besoins du présent document, les termes, définitions et symboles donnés dans l’ISO 80000-10,

l’ISO 11929-1 ainsi que les suivants s’appliquent.
© ISO 2020 – Tous droits réservés 1
---------------------- Page: 7 ----------------------
ISO 13166:2020(F)

L’ISO et l’IEC tiennent à jour des bases de données terminologiques destinées à être utilisées en

normalisation, consultables aux adresses suivantes:
— IEC Electropedia: disponible à l’adresse http:// www .electropedia .org/ ;

— ISO Online browsing platform: disponible à l’adresse https:// www .iso .org/ obp.

Tableau 1 — Symboles et définitions
Symbole Définition
232
A activité du traceur U ajouté, en becquerels, à la date du mesurage
238 235 234
c activité volumique de U, U ou U, en becquerels par litre
seuil de décision, en becquerels par litre
limite de détection, en becquerels par litre

limites basse et haute de l’intervalle élargi probabilistiquement symétrique, en becquerels par litre

cc,
< >

c , c limites basse et haute de l’intervalle élargi le plus court, en becquerels par litre

A A
R rendement total du mesurage

r , r taux de comptage du bruit de fond par seconde dans les régions d’intérêt respectives (ROI) des

0 0T
analytes de l’uranium et du traceur du spectre de l’échantillon à blanc
R rendement chimique

r , r taux de comptage brut par seconde dans les régions d’intérêt respectives (ROI) des analytes de

g gT
l’uranium et du traceur du spectre de la prise d’essai
t durée de comptage du bruit de fond, en secondes
t durée de comptage de la prise d’essai, en secondes

U incertitude élargie, calculée par U = ku(c ) avec k = 1, 2 …, en becquerels par litre

u(c ) incertitude-type associée au résultat de mesure, en becquerels par litre
V volume de la prise d’essai, en litres
ε rendement de comptage
4 Principe
232

La prise d’essai est mélangée à une aliquote de traceur U, puis mise à l’équilibre avant l’analyse.

La purification chimique de l’uranium est obtenue par une étape de concentration (par exemple une

précipitation) suivie d’une étape de séparation spécifique (par exemple par chromatographie d’échange

d’ions).

Pour le mesurage d’une prise d’essai d’environ 500 ml, la limite de détection est d’environ 5 mBq · l

pour une durée de comptage de l’ordre de 200 000 s.
230 226 228

Les radionucléides naturels tels que Th, Ra et Th peuvent être présents dans l’eau et interférer

avec le comptage des isotopes de l’uranium si aucune séparation chimique n’a été effectuée pour

éliminer ces radionucléides de la prise d’essai. Les isotopes du plutonium peuvent également interférer,

s’ils sont présents à des niveaux d’activité détectables dans l’échantillon.

La source mince mesurée est préparée par électrodéposition ou co-précipitation et mesurée par

spectrométrie alpha à l’aide d’un appareillage de type chambre à grille ou semi-conducteur. Les

mesurages reposent sur l’interaction des particules alpha avec le milieu de détection. Cette interaction

génère une charge qui est amplifiée et transmise sous forme d’une impulsion de tension proportionnelle

à l’énergie déposée de la particule alpha entrante.

L’impulsion électrique provenant du détecteur est analysée par des systèmes électroniques. Le logiciel

d’analyse de données produit un spectre montrant le nombre d’impulsions (coups) enregistrées dans

chaque intervalle d’énergie.
2 © ISO 2020 – Tous droits réservés
---------------------- Page: 8 ----------------------
ISO 13166:2020(F)

L’analyse des taux de comptage dans les fenêtres d’énergie alpha des isotopes de l’uranium permet de

238 235 234

déterminer l’activité volumique de la prise d’essai pour U, U et U, après prise en compte des

corrections liées au taux de comptage de l’essai à blanc, au volume de la prise d’essai et au rendement

total du mesurage (rendement chimique et rendement de détection).

Le rendement chimique et le rendement de détection ne sont pas nécessairement déterminés

séparément, mais sont déterminés ensemble en mesurant le rendement total du mesurage à partir du

232
taux de comptage net de U, ajouté comme traceur.

Pour quantifier toute interférence potentielle due aux réactifs, un échantillon à blanc est préparé

de la même manière que la prise d’essai. Cet échantillon à blanc est préparé en utilisant une eau de

laboratoire.

Aux fins du contrôle de la qualité, pour quantifier les impuretés potentielles dans la solution de traceur,

un autre échantillon à blanc doit être préparé en ajoutant le traceur.

Les caractéristiques radioactives des principaux isotopes de l’uranium sont données dans le Tableau 2

(Références [8], [9]).
Tableau 2 — Caractéristiques radioactives des principaux isotopes de l’uranium
Isotope de Période Énergie d’émission principale Intensité
l’uranium
années keV %
5 263,48 30,6
232 70,6 (±1,1)
5 320,24 69,1
4 783,5 13,2
233 159,1 (±0,2) × 10
4 824,2 84,3
4 722,4 28,42
234 2 455 (±0 006) × 10
4 774,6 71,37
4 366,1 18,8
235 704 (±1) × 10 4 397,8 57,19
4 414,9 3,01
4 445 26,1
236 23,43 (±0,06) × 10
4 494 73,8
4 151 22,33
238 4,468 (±0,005) × 10
4 198 77,54

Avec une résolution spectrale (FWHM, largeur totale à mi-hauteur du maximum) d’environ 20 keV

233

dans les cas les plus favorables, la spectrométrie alpha peut difficilement faire la distinction entre U

234 235 236

et U, ou U et U, en raison de la similitude de leurs énergies d’émission respectives. Toutefois,

233 236

U et U ne sont généralement pas présents dans les échantillons prélevés dans l’environnement

ou, s’ils le sont, pas en quantités supérieures à leurs limites de détection par spectrométrie alpha (voir

Annexe D).
5 Réactifs chimiques et matériel
5.1 Généralités

Les réactifs chimiques et le matériel utilisés pour le traitement chimique et la préparation de la source

sont décrits dans les Annexes A à C, qui proposent diverses alternatives. Lorsqu’il existe plusieurs

possibilités, au moins l’une d’entre elles doit être utilisée.
Utiliser uniquement des réactifs de qualité analytique reconnue.
© ISO 2020 – Tous droits réservés 3
---------------------- Page: 9 ----------------------
ISO 13166:2020(F)
5.2 Réactifs chimiques

5.2.1 Eau de laboratoire, utilisée comme blanc, aussi exempte que possible d’impuretés chimiques ou

radioactives (telles que des isotopes de l’uranium) et conforme à l’ISO 3696, qualité 3.

L’eau de pluie, recueillie récemment, est un exemple d’eau présentant une très faible activité volumique

d’uranium. L’activité volumique de l’uranium de cette eau peut être évaluée en même temps que les

interférences dues aux réactifs ou en utilisant un autre type de mesurage de précision, par exemple

l’ionisation thermique ou la spectrométrie de masse avec plasma couplé par induction.

232

5.2.2 Solution de traceur U, utilisée pour déterminer le rendement total. Elle peut également être

utilisée pour calculer le rendement chimique. La solution est préparée par dilution d’un étalon approprié

pouvant être relié à des étalons nationaux et internationaux. La solution de traceur doit être homogène

et stable.

Il convient de calculer la concentration de la solution de traceur de manière à pouvoir ajouter une faible

quantité de cette solution pour atteindre la plage d’activité de la prise d’essai. Par exemple, l’activité

−1 −1

massique de la solution de traceur pourrait être comprise entre 0,05 Bq · g et 1 Bq · g .

Il est recommandé de vérifier l’activité et la pureté de la dilution de solution de traceur avant usage

et à intervalles réguliers après sa préparation. Cette vérification peut être effectuée, par exemple,

par comptage par scintillation liquide, mais il est nécessaire de tenir compte de la re-croissance des

descendants du radionucléide. Réaliser une analyse à blanc avec le traceur est l’une des méthodes

possibles pour détecter la présence d’analytes isotopes de l’uranium dans le traceur.

228 232

Th est présent dans la solution de traceur U, car c’est un élément de sa chaîne de désintégration,

232

et a une énergie très proche de celle de U. Par conséquent, une séparation de Th et U est requise

228

(Références [10], [11]) pour réduire au minimum l’interférence de Th afin de ne pas surestimer le

232
rendement de comptage de U (voir Article 4).
5.3 Matériel
Matériel courant de laboratoire et en particulier les éléments suivants:

5.3.1 Spectromètre alpha, de type chambre à grille (avec un rendement de détection élevé, mais une

faible résolution) ou de type semi-conducteur (avec un faible rendement de détection, mais une haute

résolution). Un fonctionnement à température constante est recommandé. Suivre les instructions du

fabricant.

Pour un appareillage de type semi-conducteur, les mesurages par spectrométrie alpha dépendent de

l’interaction des particules alpha avec le silicium à implantation ionique. Cette interaction fait varier

instantanément la conductivité du silicium, proportionnellement à l’énergie de la particule alpha

entrante. Pour obtenir des spectres ayant une résolution satisfaisante, il est nécessaire de maintenir

le système de détection à une pression inférieure à 1 Pa. La résolution peut encore être améliorée en

augmentant la distance entre la source et le détecteur.
232
5.3.2 Pipette, adaptée au transfert exact de solution de traceur U (par exempl
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 13166
ISO/TC 147/SC 3
Water quality — Uranium isotopes —
Secretariat: AFNOR
Test method using alpha-spectrometry
Voting begins on:
2020­04­14
Qualité de l'eau — Isotopes de l'uranium — Méthode d'essai par
spectrométrie alpha
Voting terminates on:
2020­06­09
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/FDIS 13166:2020(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN­
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. ISO 2020
---------------------- Page: 1 ----------------------
ISO/FDIS 13166:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
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ii © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/FDIS 13166:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms, definitions and symbols ............................................................................................................................................................ 1

4 Principle ........................................................................................................................................................................................................................ 2

5 Chemical reagents and equipment .................................................................................................................................................... 3

5.1 General ........................................................................................................................................................................................................... 3

5.2 Chemical reagents ................................................................................................................................................................................ 3

5.3 Equipment ................................................................................................................................................................................................... 4

6 Sampling and samples .................................................................................................................................................................................... 4

6.1 Sampling ....................................................................................................................................................................................................... 4

6.2 Sample storage ........................................................................................................................................................................................ 4

7 Separation and measurement ................................................................................................................................................................ 5

7.1 Chemical steps ......................................................................................................................................................................................... 5

7.2 Measurement ............................................................................................................................................................................................ 5

7.2.1 Quality control ................................................................................................................................................................... 5

7.2.2 Chemical yield .................................................................................................................................................................... 5

7.2.3 Background........................................................................................................................................................................... 5

8 Expression of results ........................................................................................................................................................................................ 6

8.1 Spectrum analysis ................................................................................................................................................................................ 6

8.2 Calculation of activity concentration ................................................................................................................................... 6

8.3 Standard uncertainty ......................................................................................................................................................................... 6

8.4 Decision threshold ............................................................................................................................................................................... 7

8.5 Detection limit ......................................................................................................................................................................................... 7

8.6 Limits of the coverage interval .................................................................................................................................................. 8

8.6.1 Limits of the probabilistically symmetric coverage interval...................................................... 8

8.6.2 The shortest coverage interval ............................................................................................................................ 8

9 Test report ................................................................................................................................................................................................................... 9

Annex A (informative) Chemical separation of uranium ..............................................................................................................10

Annex B (informative) Precipitation of the source by electrodeposition ...................................................................13

Annex C (informative) Preparation of the source by coprecipitation .............................................................................16

Annex D (informative) Occurrence of uranium isotopes ..............................................................................................................18

Bibliography .............................................................................................................................................................................................................................19

© ISO 2020 – All rights reserved iii
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ISO/FDIS 13166:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non­governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: www .iso .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 3,

Radiological methods.

This second edition cancels and replaces the first edition (ISO 13166:2014), of which it constitutes a

minor revision. The changes compared to the previous edition are as follows:
— Update of the common introduction.
— Update of the text considering the new ISO 11929 series published in 2019.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved
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ISO/FDIS 13166:2020(E)
Introduction

Radioactivity from several naturally occurring and anthropogenic sources is present throughout

the environment. Thus, water bodies (e.g. surface waters, ground waters, sea waters) can contain

radionuclides of natural, human­made, or both origins:
40 3 14

— Natural radionuclides, including K, H, C, and those originating from the thorium and uranium

226 228 234 238 210

decay series, in particular Ra, Ra, U, U, and Pb, can be found in water for natural reasons

(e.g. desorption from the soil and wash off by rain water) or can be released from technological

processes involving naturally occurring radioactive materials (e.g. the mining and processing of

mineral sands or phosphate fertilizer production and use);

— Human­made radionuclides, such as transuranium elements (americium, plutonium, neptunium,

3 14 90

curium), H, C, Sr, and gamma emitting radionuclides can also be found in natural waters.

Small quantities of these radionuclides are discharged from nuclear fuel cycle facilities into the

environment as the result of authorized routine releases. Some of these radionuclides used for

medical and industrial applications are also released into the environment after use. Anthropogenic

radionuclides are also found in waters as a result of past fallout contaminations resulting from

the explosion in the atmosphere of nuclear devices and accidents such as those that occurred in

Chernobyl and Fukushima.

Radionuclide activity concentration in water bodies can vary according to local geological

characteristics, and climatic conditions and can be locally and temporally enhanced by releases from

[1]

nuclear installation during planned, existing and emergency exposure situations . Drinking­water

may thus contain radionuclides at activity concentrations which could present a risk to human health.

The radionuclides present in liquid effluents are usually controlled before being discharged into

[2]

the environment and water bodies. Drinking water is monitored for its radioactivity content as

[3]

recommended by the World Health Organization (WHO) so that proper actions can be taken to ensure

that there is no adverse health effects to the public. Following these international recommendations,

national regulation usually specify radionuclide authorized concentration limits for liquid effluent

discharged to the environment and radionuclide guidance levels for water bodies and drinking waters

for planned, existing and emergency exposure situations. Compliance with these limits can be assessed

using measurement results with their associated uncertainties as specified by ISO/IEC Guide 98-3 and

[4]
ISO 5667­20 .

Depending on the exposure situation, there are different limits and guidance levels that would result

in an action to reduce health risk. As an example, during a planned or existing situation, the WHO

guidance level in drinking water for uranium-238 and uranium-234 is 10 and 1 Bq · l , respectively. The

provisional guideline value for the concentration of uranium in drinking water is 30 μg · l based on its

chemical toxicity, which is predominant compared with its radiological toxicity.

NOTE 1 The guidance level is the activity concentration with an intake of 2 l/d of drinking water for one year

that results in an effective dose of 0,1 mSv/a for members of the public. This is an effective dose that represents a

[3]

very low level of risk and which is not expected to give rise to any detectable adverse health effects .

[5]

In the event of a nuclear emergency, the WHO Codex Guideline Levels mentioned that the activity

concentration might be greater.

NOTE 2 The Codex guidelines levels (GLs) apply to radionuclides contained in foods destined for human

consumption and traded internationally, which have been contaminated following a nuclear or radiological

emergency. These GLs apply to food after reconstitution or as prepared for consumption, i.e., not to dried or

concentrated foods, and are based on an intervention exemption level of 1 mSv in a year for members of the

[5]
public (infant and adult) .

Thus, the test method can be adapted so that the characteristic limits, decision threshold, detection

limit and uncertainties ensure that the radionuclide activity concentrations test results can be verified

to be below the guidance levels required by a national authority for either planned/existing situations

[6][7]
or for an emergency situation .
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ISO/FDIS 13166:2020(E)

Usually, the test methods can be adjusted to measure the activity concentration of the radionuclide(s)

in either wastewaters before storage or in liquid effluents before being discharged to the environment.

The test results will enable the plant/installation operator to verify that, before their discharge,

wastewaters/liquid effluent radioactive activity concentrations do not exceed authorized limits.

The test method(s) described in this document may be used during planned, existing and emergency

exposure situations as well as for wastewaters and liquid effluents with specific modifications that

could increase the overall uncertainty, detection limit, and threshold.

The test method(s) may be used for water samples after proper sampling, sample handling, and test

sample preparation (see the relevant part of the ISO 5667 series).

This document has been developed to answer the need of test laboratories carrying out these

measurements that are sometimes required by national authorities, as they may have to obtain a

specific accreditation for radionuclide measurement in drinking water samples.

This document is one of a family of International Standards on test methods dealing with the

measurement of the activity concentration of radionuclides in water samples.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 13166:2020(E)
Water quality — Uranium isotopes — Test method using
alpha-spectrometry

WARNING — Persons using this document should be familiar with normal laboratory practices.

This document does not purport to address all of the safety problems, if any, associated with its

use. It is the responsibility of the user to establish appropriate safety and health practices and to

determine the applicability of any other restrictions.

IMPORTANT — It is absolutely essential that tests conducted according to this document be

carried out by suitably trained staff.
1 Scope

This document specifies the conditions for the determination of uranium isotope activity concentration

in samples of environmental water (including sea waters) using alpha-spectrometry and 232U as a

yield tracer.

A chemical separation is required to separate and purify uranium from a test portion of the sample.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 3696, Water for analytical laboratory use — Specification and test methods

ISO 5667­1, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes and

sampling techniques

ISO 5667­3, Water quality — Sampling — Part 3: Preservation and handling of water samples

ISO 11929­1, Determination of the characteristic limits (decision threshold, detection limit and limits of

the coverage interval) for measurements of ionizing radiation — Fundamentals and application — Part 1:

Elementary applications

ISO 11929­3, Determination of the characteristic limits (decision threshold, detection limit and limits of

the coverage interval) for measurements of ionizing radiation — Fundamentals and application — Part 3:

Applications to unfolding methods
ISO 80000­10, Quantities and units — Part 10: Atomic and nuclear physics

ISO/IEC Guide 98­3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in

me a s ur ement (GUM: 1995)

ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories

3 Terms, definitions and symbols

For the purposes of this document, the terms, definitions, and symbols given in ISO 80000-10,

ISO 11929-1 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at http:// www .electropedia .org/
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ISO/FDIS 13166:2020(E)
— ISO Online browsing platform: available at http:// www .iso .org/ obp
Table 1 — Symbols and definitions
Symbol Definition
232
A activity of U tracer added, in becquerel, at the date of measurement
238 235 234
c activity concentration of U or U or U, in becquerel per litre
decision threshold, in becquerel per litre
# detection limit, in becquerel per litre

lower and upper limits of the probabilistically symmetric coverage interval, in becquerel per litre

cc,
< >

c , c lower and upper limits of the shortest coverage interval, in becquerel per litre

A A
R total measurement yield

r , r background count rate per second for the uranium analytes and tracer in the respective regions

0 0T
of interest (ROI) of the blank sample spectrum
R chemical yield

r , r gross count rate per second for the uranium analytes and tracer in the respective regions of

g gT
interest (ROI) of the test sample spectrum
t background counting time, in seconds
t sample counting time, in seconds

U expanded uncertainty, calculated by U = ku(c ) with k = 1, 2 …, in becquerel per litre

u(c ) standard uncertainty associated with the measurement result; in becquerel per litre

V volume of test sample, in litres
ε counting efficiency
4 Principle
232

The test sample is mixed with an aliquot of U tracer, followed by equilibration of the sample prior

to analysis. Chemical isolation of uranium is achieved by a concentration step (e.g. a precipitation)

followed by a specific separation step (e.g. using ion exchange chromatography).

The detection limit for measurement of a test portion of about 500 ml is approximately 5 mBq · l with

a counting time of about 200 000 s.
230 226 228

Natural radionuclides such as Th, Ra and Th can be present in water and can interfere with the

counting of uranium isotopes if no chemical separation is carried out to remove these radionuclides from

the test portion. Plutonium isotopes can also interfere, if present with detectable activities in the sample.

The measured thin source is prepared by electrodeposition or coprecipitation and measured by alpha-

spectrometry using a grid chamber or a semiconductor-type apparatus. Measurements rely on the

interaction of alpha­particles with the detecting medium. This interaction creates a charge, which is

amplified and output as a voltage pulse proportional to the deposited energy of the incoming alpha-

particle.

The electric pulse from the detector is analysed by the electronic systems. Data analysis software

provides a spectrum, in which the number of pulses (counts) recorded in each energy interval is shown.

The analysis of the count rates in the uranium isotopes alpha-energy windows allows the determination

238 235 234

of the test sample activity concentration for U, U and U, after correcting for the blank count rate,

volume of the test sample and the total measurement yield (chemical yield and detection efficiency).

The chemical yield and detection efficiency are not necessarily determined separately, but are

232

determined together by measuring the total measurement yield from the net count rate of U, added

as a chemical yield tracer.
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ISO/FDIS 13166:2020(E)

In order to quantify any potential interference coming from the reagents, a blank sample is prepared in

the same way as the test sample. This blank sample is prepared using a laboratory water.

For quality control, in order to quantify potential impurities in the tracer solution, another blank sample

shall be prepared with addition of tracer.

The radioactive characteristics of the main uranium isotopes are given in Table 2 (References [8], [9]).

Table 2 — Radioactive characteristics of the main uranium isotopes
Uranium Half-life Main emission energy Intensity
isotope years keV %
5 263,48 30,6
232 70,6 (±1,1)
5 320,24 69,1
4 783,5 13,2
233 159,1 (±0,2) × 10
4 824,2 84,3
4 722,4 28,42
234 2,455 (±0,006) × 10
4 774,6 71,37
4 366,1 18,8
235 704 (±1) × 10 4 397,8 57,19
4 414,9 3.01
4 445 26,1
236 23,43 (±0,06) × 10
4 494 73,8
4 151 22,33
238 4,468(±0,005) × 10
4 198 77,54

With a spectral resolution (FWHM full-width half-maximum height) of around 20 keV in best cases,

233 234 235 236

alpha-spectrometry cannot easily resolve U and U, nor U and U, due to the similarity in

233 236

their respective emission energies. However, U and U are normally not present in environmental

samples or in quantities above their detection limits using alpha spectrometry (see Annex D).

5 Chemical reagents and equipment
5.1 General

The chemical reagents and equipment used for chemical treatment and preparation of the source are

described in Annexes A to C, which give various alternatives. Where there are options, at least one of

the options presented shall be used.
Use only reagents of recognized analytical grade.
5.2 Chemical reagents

5.2.1 Laboratory water, used as a blank, as free as possible of chemical or radioactive impurities

(e.g. uranium isotopes), conforming to ISO 3696, grade 3.

Fresh rainwater is an example of water with a very low uranium activity concentration. The uranium

activity concentration of this water can be evaluated at the same time as interferences from reagents or

using another type of precise measurement, e.g. thermal ionization or inductively coupled plasma mass

spectrometry.
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ISO/FDIS 13166:2020(E)
232

5.2.2 U tracer solution, used to determine the total yield. It can also be used to calculate the chemical

yield. The solution is prepared by the dilution of a suitable standard that provides traceability to national

and international standards. The tracer solution shall be homogeneous and stable.

The tracer solution concentration should be calculated to allow adding a small amount of this solution

in order to be in the range of activity contained in the test portion. For example, the tracer solution

−1 −1
concentration could be between 0,05 Bq · g and 1 Bq · g .

It is recommended that the activity and the purity of the tracer solution dilution be checked before

use and at regular intervals after preparation. This can be done, for example, by liquid scintillation

counting, but account needs to be taken of progeny radionuclide ingrowth. Performing a blank analysis

with tracer is a potential way to identify any presence of uranium isotope analytes in the tracer.

228 232

Th is present in the U tracer solution as a member of its decay series and has very close energy to

232

that of U. Therefore, separation between Th and U is required (References [10], [11]) to minimize the

228 232

interference of Th so that the counting yield of U is not overestimated (see Clause 4).

5.3 Equipment
Usual laboratory apparatus and in particular the following:

5.3.1 Alpha-spectrometer, of the grid chamber (with higher detection yield, but lower resolution)

or semiconductor type (with lower detection yield, but higher resolution). Operation at constant

temperature is recommended. Follow the manufacturer's instructions.

For semiconductor-type apparatus, the measurements using alpha-spectrometry depend on the

interaction of alpha-particles with ion-implanted silicon. This interaction instantly changes the

conductivity of the silicon, proportional to the energy of the incoming alpha-particle. To achieve well-

resolved spectra, the detection system needs to be maintained at a pressure <1 Pa. Resolution can be

further enhanced through increasing distance between source and detector.
232

5.3.2 Pipette, suitable for the accurate transfer of (for example 100 µl) U tracer solution with a total

precision within ±1 %.
5.3.3 Balance, for example, capable of achieving ±0,1 mg precision.
6 Sampling and samples
6.1 Sampling
Conditions of sampling shall conform to ISO 5667­1.

Filter the sample to remove solids and then acidify to < pH 2 with nitric acid or hydrochloric acid as soon

as possible after sampling prior to analysis, as specified in ISO 5667-3. Acidification prior to filtration

can result in leaching of uranium from solids component of sample.

It is important that the laboratory receive a representative sample, unmodified during transport or

storage and in an undamaged container.
6.2 Sample storage
If required, the sample is shall be stored according to ISO 5667-3.
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ISO/FDIS 13166:2020(E)
7 Separation and measurement
7.1 Chemical steps

Suggested separation and source preparation strategies are outlined in Annexes A, B, and C respectively.

7.2 Measurement
7.2.1 Quality control

Equipment quality control sources shall be measured to verify that the measurement equipment is

performing within agreed limits.
239/240 230 239 244 241
A thin source of Pu (other alpha­emitters such as Th, Pu, Cm, and Am are also

possible) may be employed to check the energy calibration and the energy resolution (alpha-emissions

are in the 5,10 MeV to 5,20 MeV energy region), and there is no appreciable decay over the working life

of the source.
7.2.2 Chemical yield

The chemical yield can be considered as a quality control parameter. In general, the chemical yield

obtained is around 90 %. For very low chemical yields, it is recommended to redo the sample analysis.

The chemical yield R of the process can be calculated using Formula (1):
R = (1)

Total yield R is the product of the chemical yield and the counting efficiency ε.

Total yield, R, is calculated from the sample spectrum using Formula (2):
rr−
gT 0T
R= (2)
7.2.3 Background

The background rate of each detector is determined with an empty source support with the lowest

activity possible present on, this shall take at least as much time as the counting of a sample.

The optimum time for the measurement of the background source can be shown to be equal to that of

the source from very low activity sources.
The blank sample
...

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